Density-functional study of (formula presented) defects in alkali halides

Abstract

Density-functional methods, as implemented in the Amsterdam Density Functional program, are used to calculate the electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) parameters of the (formula presented) defect in a halide monovacancy in various alkali halides (formula presented) K, Rb and (formula presented) Br, I) lattices. The calculations were performed on cluster in vacuo models for the defect and its lattice surroundings, involving up to 88 atoms in order to limit boundary effects. For all (formula presented) lattices, the calculated g and (formula presented) hyperfine tensors of the (formula presented) molecular ion are in very good agreement with the available EPR data, explicitly supporting the monovacancy model for the defect. In addition, computational results for the principal superhyperfine and quadrupole values and axes of the nearest shells of (formula presented) ions are compared with experimental ENDOR data. The merits and shortcomings of the applied cluster in the vacuo method are critically evaluated. © 2002 The American Physical Society.